A hybrid electro-mechanical vehicular transmission utilizes interactive differential gear arrangements that are operatively connected to an engine and typically two motor/generators. Selective utilization of torque transfer devices enables power transfer via the differential gear arrangements from the engine and/or motor/generators to the output member of the transmission.
A power transmission in an electro-mechanical transmission is described in commonly owned U.S. Provisional Application No. 60/590,427 entitled Electrically Variable Transmission with Selective Fixed Ratio Operation, filed Jul. 22, 2004, and hereby incorporated by reference in its entirety.
Hybrid system motor/generators, especially those for strong hybrid systems, must be high powered. Because limited packaging space is available within the transmission structure, the motor/generators require very high power density. High power density motor/generators produce a large amount of heat during operation. The stator of the motor/generator, with its high density electrical windings particularly produces a large amount of heat resulting in the need to control the temperature of the stator to ensure continuous and stable operation.